Vehicles operating in an autonomous mode (e.g., driverless) can relieve occupants, especially the driver, from some driving-related responsibilities. When operating in an autonomous mode, the vehicle can navigate to various locations using onboard sensors, allowing the vehicle to travel with minimal human interaction or in some cases without any passengers.
Motion planning and control are critical operations in autonomous driving. Particularly, trajectory planning is a critical component in an autonomous driving system. Conventional trajectory planning techniques rely heavily on high-quality reference lines, which are guidance paths, e.g., a center line of a road, for autonomous driving vehicles, to generate stable trajectories. Usually, the map data (typically a sequence of two-dimensional (2D) points in the world frame) directly from sensors cannot provide the required smoothness, and therefore directly using the map data may cause the planners generating unstable and oscillating trajectories between planning cycles.